Gate structure integration scheme for fin field effect transistors

ABSTRACT

In one embodiment, a semiconductor device is provided that includes a gate structure present on a channel portion of a fin structure. The gate structure includes a dielectric spacer contacting a sidewall of a gate dielectric and a gate conductor. Epitaxial source and drain regions are present on opposing sidewalls of the fin structure, wherein surfaces of the epitaxial source region and the epitaxial drain region that is in contact with the sidewalls of the fin structure are aligned with an outside surface of the dielectric spacer. In some embodiments, the dielectric spacer, the gate dielectric, and the gate conductor of the semiconductor device are formed using a single photoresist mask replacement gate sequence.

BACKGROUND

1. Technical Field

The present disclosure relates to semiconductor devices, such assemiconductor devices including fin structures.

2. Description of the Related Art

The dimensions of semiconductor field effect transistors (FETs) havebeen steadily shrinking over the last thirty years or so, as scaling tosmaller dimensions leads to continuing device performance improvements.Planar FET devices typically have a conducting gate electrode positionedabove a semiconducting channel that is electrically isolated from thechannel by a thin layer of gate oxide. Current through the channel iscontrolled by applying voltage to the conducting gate. With conventionalplanar FET scaling reaching fundamental limits, the semiconductorindustry is looking at more unconventional geometries that willfacilitate continued device performance improvements. One such class ofdevice is a fin field effect transistor (finFET).

SUMMARY

In one aspect, a method is disclosed for forming a semiconductor devicethat includes depositing a dielectric layer over a fin structure, andforming a sacrificial structure on a portion of the dielectric layer, inwhich the sacrificial structure includes a mandrel portion and a spacermask portion. The dielectric layer is then etched using the sacrificialstructure as an etch mask. Source and drain structures are formed onopposing sides of a portion of the fin structure that the sacrificialstructure is present on. The mandrel portion of the sacrificialstructure is removed, and the dielectric layer is etched selective tothe spacer mask portion. A remaining portion of the dielectric layerprovides a gate sidewall spacer on opposing sides of the fin structure.A gate structure is formed on a channel region portion of the finstructure in contact with the gate sidewall spacer.

In another embodiment, a method of forming a semiconductor device isprovided that includes depositing a dielectric layer over a plurality offin structures, and forming a plurality of sacrificial structures on aportion of the dielectric layer. Each sacrificial structure of theplurality of sacrificial structures includes a mandrel portion and aspacer mask portion. The plurality of fin structures is etchedselectively to the plurality of sacrificial structures to expose asidewall portion of the plurality of fin structures. Source and drainstructures are formed on the sidewall portion of the plurality of finstructures. The mandrel portion of the plurality of sacrificialstructures may then be removed. The dielectric layer is etched selectiveto the spacer mask portion. A remaining portion of the dielectric stackprovides the gate sidewall spacers. A gate structure is formed on achannel region portion of each of the plurality of fin structures, inwhich the gate structure is in contact with the gate sidewall spacers.

In another aspect, the present disclosure provides a semiconductordevice including a fin structure. In one embodiment, the semiconductordevice includes a gate structure that is present on a channel regionportion of a fin structure. The gate structure includes a gate sidewallspacer contacting a sidewall of a gate dielectric and a gate conductor.An epitaxial source region and an epitaxial drain region are present onopposing sidewalls of the fin structure. The surfaces of the epitaxialsource region and the epitaxial drain region that are in contact withthe sidewalls of the fin structure are aligned with an outside surfaceof the gate sidewall spacer.

BRIEF DESCRIPTION OF DRAWINGS

The following detailed description, given by way of example and notintended to limit the disclosure solely thereto, will best beappreciated in conjunction with the accompanying drawings, wherein likereference numerals denote like elements and parts, in which:

FIG. 1A is a top down view depicting forming a plurality of finstructures from a bulk semiconductor substrate, in accordance with oneembodiment of the present disclosure.

FIG. 1B is a side cross-sectional view along section line A-A of thestructure depicted in FIG. 1A.

FIG. 2A is a top down view depicting forming isolation regions adjacentto the fin structures, in accordance with one embodiment of the presentdisclosure.

FIG. 2B is a side cross-sectional view along section line A-A of thestructure depicted in FIG. 2A, which is hereafter referred to as across-section perpendicular to the length of the fin structures.

FIG. 2C is a side cross-sectional view along section line B-B of thestructure depicted in FIG. 2A, which is hereafter referred to as across-section parallel to the length of the fin structures.

FIG. 3 is a side cross-sectional view perpendicular to the finstructures, i.e., as along section line A-A in FIG. 1B, depictingforming a dielectric layer on the fin structures, in accordance with thepresent disclosure.

FIG. 4A is a side cross-sectional view perpendicular to the finstructures depicting forming a material layer stack for a sacrificialstructure for defining a gate structure and gate sidewall spacers, inaccordance with one embodiment of the present disclosure.

FIG. 4B is a side cross-sectional view parallel to the fin structures ofthe structure depicted in FIG. 4A.

FIG. 5A is a side cross-sectional view perpendicular to the finstructures of patterning a mandrel portion of the sacrificial structure,in accordance with one embodiment of the present disclosure.

FIG. 5B is a side cross-sectional view parallel to the fin structures ofthe structure depicted in FIG. 5A.

FIG. 6A is a side cross-sectional view perpendicular to the finstructures of forming a spacer mask portion of the sacrificialstructure, in accordance with one embodiment of the present disclosure.

FIG. 6B is a side cross-sectional view parallel to the fin structures ofthe structure depicted in FIG. 6A.

FIG. 7A is a side cross-sectional view perpendicular to the finstructures depicting etching the dielectric layer using the sacrificialstructure as an etch mask, in accordance with one embodiment of thepresent disclosure.

FIG. 7B is a side cross-sectional view parallel to the fin structures ofthe structure depicted in FIG. 7A.

FIG. 8 is a side cross-sectional view parallel to the fin structuresdepicting one embodiment of etching exposed portions of the finstructures using the sacrificial structure as an etch mask to exposesidewalls of the fin structures, and forming source and drain regions onthe sidewalls of the fin structures, in accordance with the presentdisclosure.

FIG. 9 is a side cross-sectional view parallel to the fin structuresdepicting one embodiment of forming a dielectric fill between adjacentpillars of dielectric material that remain following etching of thedielectric layer selectively to the sacrificial structures, inaccordance with one embodiment of the present disclosure.

FIG. 10 is a side cross-sectional view parallel to the fin structures ofremoving the mandrel portion of the sacrificial structure, in accordancewith one embodiment of the present disclosure.

FIG. 11 is a side cross-sectional view parallel to the fin structures ofetching the dielectric layer selectively to the spacer mask portion toform the gate sidewall spacer of the gate structure, in accordance withone embodiment of the present disclosure.

FIG. 12 is a side cross-sectional view parallel to the fin structures ofremoving the spacer mask portion of the sacrificial structure, inaccordance with one embodiment of the present disclosure.

FIG. 13 is a side cross-section view parallel to the fin structures offorming gate structures on the channel region portion of the finstructures, in accordance with one embodiment of the present disclosure.

FIG. 14 is a perspective view of one embodiment of fin field effecttransistors (finFETs) formed using the method depicted in FIGS. 1-13, inaccordance with the present disclosure.

FIG. 15 is a magnified view of the section identified in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and details disclosed hereinare not to be interpreted as limiting, but merely as a representativebasis for teaching one skilled in the art to variously employ themethods and structures of the present disclosure. For purposes of thedescription hereinafter, the terms “upper”, “lower”, “right”, “left”,“vertical”, “horizontal”, “top”, “bottom”, and derivatives thereof shallrelate to the embodiments of the disclosure, as it is oriented in thedrawing figures. The terms “positioned on” means that a first element,such as a first structure, is present on a second element, such as asecond structure, wherein intervening elements, such as an interfacestructure, e.g. interface layer, may be present between the firstelement and the second element. The term “direct contact” means that afirst element, such as a first structure, and a second element, such asa second structure, are connected without any intermediary conducting,insulating or semiconductor layers at the interface of the two elements.

In some embodiments, the methods and structures disclosed herein providefin field effect transistors. A “field effect transistor (FET)” is asemiconductor device in which the output current, i.e., source-draincurrent, is controlled by the voltage applied to the gate. A FET hasthree terminals, i.e., gate structure, source region and drain region. Agate structure is a structure used to control output current (i.e., flowof carriers in the channel) of a semiconducting device throughelectrical or magnetic fields. A finFET is a field effect transistor inwhich at least the channel region portion of the field effect transistoris present in a fin structure. The channel region portion is the regionunderlying the gate structure and between the source and drain of asemiconductor device that becomes conductive when the semiconductordevice is turned on.

In the prior finFET manufacturing, the integration process typicallyincludes a sequence of (1) fin formation; (2) dummy gate formation (alsoreferred to sacrificial gate or replacement gate); (3) gate sidewallspacer formation; (4) source and drain epitaxial merging of the finstructures; (5) replacement of the dummy gate with a functional gatestructure; and (6) self-aligned contact formation. The prior finFETmanufacture process results in a variation in gate pitch, i.e., gatecritical dimension variation, as well as resulting in contact to gateoverlay errors. Furthermore, the multiple etch steps required forforming the gate sidewall spacer, and removing the dummy gatestructures, can result in fin erosion and damage. For example, the gatesidewall spacer etch steps may result in insufficient spacer removalbetween the fin structures, which can result in insufficient depositionsurfaces for the epitaxial merge of the source and drain regions.Further, the dummy gate top corners may also be exposed by the spaceretch, which can result in the formation of epitaxial nodules. Epitaxialnodules occur during the epitaxial growth in the source and drainregion, wherein the gate conductor that consists of polycrystallinesilicon if not fully encapsulated by silicon nitride spacer provides thesite for epitaxial growth on the gate conductor to result in theformation of epitaxial nodules, as well as leading to gate conductor tosource and drain region shorts.

In some embodiments, the methods and structures that are disclosedherein provide that the source and drain epitaxial merge structures, thegate structure and gate sidewall spacer are all defined by a singlesidewall image transfer technique. For example, in some embodiments, thegate area, i.e., gate structure and gate dielectric, can be defined by amandrel portion of a sacrificial structure, while the epitaxial sourceand drain merge portions will be defined by the non-mandrel spacingbetween two gate sidewall spacers, and the gate sidewall spacers will bedefined by the sidewall image transfer (SIT) spacer, i.e., gate maskportion of the sacrificial structure, that is present on the sidewallsof the mandrel portion. By employing a single sidewall image transfertechnique, the fin erosion that results from the etch processes forremoving a dummy gate structure and gate sidewall spacer formation oftypical finFET formation methods can be reduced. Further, the methodsand structures disclosed herein reduce the concentration of defects inthe source and drain epitaxial merge regions, and minimizes theformation of epitaxial nodules at the gate corners. In some embodiments,the structures and methods disclosed herein provide an integrationscheme where the gate structure, the gate sidewall spacer and the sourceand drain epitaxial merge regions are defined by the same patterningprocess. The methods and structures of the present disclosure are nowdescribed in more detail with reference to FIGS. 1-15.

FIGS. 1A and 1B depict one embodiment of forming a plurality of finstructures 10 from a bulk semiconductor substrate 5. A “bulksemiconductor substrate” is a substrate that is composed of a singlesemiconductor material. A bulk semiconductor substrate 5 does notinclude a buried dielectric layer that is typically present in siliconon insulator (SOI) substrates. The semiconductor material that providesthe bulk semiconductor substrate 5 may be a semiconducting materialincluding, but not limited to, silicon, strained silicon, a siliconcarbon alloy (e.g., silicon doped with carbon (Si:C), silicon germanium,a silicon germanium and carbon alloy (e.g., silicon germanium doped withcarbon (SiGe:C), silicon alloys, germanium, germanium alloys, galliumarsenic, indium arsenic, indium phosphide, as well as other III/V andII/VI compound semiconductors.

The plurality of fin structures 10 may be formed from the bulksemiconductor substrate 5 using photolithography and etch processes. Asused herein, the term “fin structure” refers to a semiconductormaterial, which is employed as the body of a semiconductor device, inwhich the gate structure is positioned around the fin structure suchthat charge flows down the channel on the two sidewalls of the finstructure and optionally along the top surface of the fin structure. Inone example, to form the fin structures 10, a photoresist mask is formedoverlying the bulk semiconductor substrate 5, in which the portion ofthe bulk semiconductor substrate 5 that is underlying the photoresistmask provides the plurality of fin structures 10. The portion of thebulk semiconductor substrate 5 that is not protected by the photoresistmask is removed using a selective etch process. To provide thephotoresist mask, a photoresist layer is first positioned on the bulksemiconductor substrate 5. The photoresist layer may be provided by ablanket layer of photoresist material that is formed utilizing adeposition process such as, e.g., plasma enhanced CVD (PECVD),evaporation or spin-on coating. The blanket layer of photoresistmaterial is then patterned to provide the photoresist mask utilizing alithographic process that may include exposing the photoresist materialto a pattern of radiation and developing the exposed photoresistmaterial utilizing a resist developer. Following the formation of thephotoresist mask, an etching process may remove the unprotected portionsof the bulk semiconductor substrate 5 selectively to the photoresistmask. For example, the transferring of the pattern provided by thephotoresist into the underlying structures may include an anisotropicetch. As used herein, an “anisotropic etch process” denotes a materialremoval process in which the etch rate in the direction normal to thesurface to be etched is greater than in the direction parallel to thesurface to be etched. The anisotropic etch may include reactive-ionetching (RIE). Other examples of anisotropic etching that can be used atthis point of the present disclosure include ion beam etching, plasmaetching or laser ablation. The etch process may be timed to determinethe height H₁ of the fin structures 10.

Each of the fin structures 10 may have a height H₁ ranging from 5 nm to200 nm. In another embodiment, each of the fin structures 10 has aheight H₁ ranging from 10 nm to 100 nm. In one example, each of the finstructures 10 has a height H₁ ranging from 20 nm to 50 nm. Each of theplurality of fin structures 10 may have a width W₁ of less than 20 nm.In another embodiment, each of the fin structures 10 has a width W₁ranging from 3 nm to 8 nm. Although six fin structures 10 are depictedin FIGS. 1A and 1B, the present disclosure is not limited to only thisexample. It is noted that any number of fin structures 10 may be formedfrom the bulk semiconductor substrate 5. The pitch P₁ separatingadjacent fin structures in the plurality of fin structures 10 may rangefrom 15 nm to 200 nm. In another example, the pitch P₁ separatingadjacent fin structures 10 may range from 15 nm to 100 nm.

FIGS. 2A-2C depict one embodiment of forming isolation regions 15adjacent to the fin structures 10. In some embodiments, the isolationregions 15 may be composed of a dielectric material, such as an oxide,nitride or oxynitride dielectric. For example, in some embodiments, whenthe isolation regions 15 are composed of an oxide, the oxide may besilicon oxide (SiO₂), and when the isolation regions 15 are composed ofa nitride, the nitride may be silicon nitride (Si₃N₄). Other examples ofmaterials that may be employed for the isolation regions 15 includesilicon oxynitride, hafnium oxide, hafnium oxynitride, alumina andcombinations thereof. The isolation regions 15 may also be formed usingCVD, PECVD, high-density plasma CVD (HPCVD), chemical solutiondeposition or a spin-on glass process. In some embodiments, followingdeposition, the material of the isolation regions 15 may be recessed byan etch process, such as an anisotropic or isotropic etch process. Forexample, the isolation regions 15 may be recessed using reactive ionetch. The isolation regions 15 may be recessed to have a height H₂ thatis less than half the height H₁ of the fin structures 10. In someembodiments, the isolation regions 15 may be recessed to have a heightH₂ that is less than a quarter of the height of the fin structures 10.

FIG. 3 depicts one embodiment of forming at least one dielectric layer20 on the fin structures 10 and the isolation regions 15. In someembodiments, the composition of the at least one dielectric layer 20 isselected to provide the composition of the later formed gate sidewallspacers that are present on the sidewalls of the gate structure that issubsequently formed on the channel region portion of the fin structures10. In some embodiments, the composition of the at least one dielectriclayer 20 is selected so that it may be removed selectively to thematerial of the fin structures 10, and the material of the isolationregions 15. In some embodiments, the at least one dielectric layer 20may be composed of a dielectric material, such as an oxide, nitride oroxynitride dielectric. For example, in some embodiments, when the atleast one dielectric layer 20 is composed of an oxide, the oxide may besilicon oxide (SiO₂), and when the at least one dielectric layer 20 iscomposed of a nitride, the nitride may be silicon nitride (Si₃N₄). Otherexamples of materials that may be employed for the at least onedielectric layer 20 include silicon oxynitride, hafnium oxide, hafniumoxynitride, alumina and combinations thereof. In some other examples,the at least one dielectric layer 20 may be comprised of siliconcarbides (SiCN), silicon carbonitrides, silsequioxanes, siloxanes, boronphosphate silicate glass (BPSG) and combinations thereof. In oneexample, when the fin structures 10 are composed of silicon (Si) and theisolation regions 15 are composes of silicon oxide (SiO₂), the at leastone dielectric layer 20 may be composed of silicon nitride (Si₃N₄).

In some embodiments, the at least one dielectric layer 20 may be formedusing a deposition process, such as chemical vapor deposition (CVD).Variations of CVD processes that are suitable for forming the at leastone dielectric layer 20 include, but are not limited to, atmosphericpressure CVD (APCVD), low pressure CVD (LPCVD) and plasma enhanced CVD(PECVD), metal organic CVD (MOCVD) and combinations thereof may also beemployed. The at least one dielectric layer 20 may also be formed usingthermal growth, such as oxidation and/or nitridation, chemical solutiondeposition or a spin-on glass process.

The at least one dielectric layer 20 may be a single layer or amulti-layered structure. The thickness of the at least one dielectriclayer 20 is typically selected to provide a height of the gate sidewallspacer. For example, the thickness of the at least one dielectric layer20 may range from 20 nm to 50 nm. In another example, the at least onedielectric layer 20 may have a thickness ranging from 30 nm to 40 nm.

FIGS. 4A and 4B depict one embodiment of forming a material layer stack25 (hereafter referred to as “SIT material layer stack 25”) for sidewallimage transfer (SIT) processing on the at least one dielectric layer 20.The SIT material layer stack 25 is subsequently processed to provide thesacrificial structure including the mandrel portion and the spacer maskportion. By “sacrificial” it is meant that the structure is used informing the semiconductor devices disclosed herein, but is not presentin the final device structure. In some embodiments, the SIT materiallayer stack 25 may include an oxide containing layer 26, an amorphoussemiconductor containing layer 27, a metal nitride layer 28, and anorganic planarizing layer 29. It is noted that the SIT material layerstack 25 that is described above is only one example of a material layerstack suitable for use with the methods and structures disclosed herein.The present disclosure is not limited to only this example, as othercompositions have also been contemplated for use with the SIT materiallayer stack 25. Additionally, other material layers may be incorporatedinto the SIT material layer stack 25 that are not specifically depictedin FIGS. 4A and 4B. Further, one or more of the material layers that aredepicted in the SIT material layer stack 25 may be omitted.

In one embodiment, the oxide containing layer 26 may be composed ofsilicon oxide (SiO₂) or silicon oxynitride. The oxide containing layer26 may be formed using thermal growth or deposition processes. Forexample, the oxide containing layer 26 may be formed using thermaloxidation, which includes annealing in an oxygen containing environment.In other examples, the oxide containing layer 26 may be formed usingCVD, such as PECVD. The oxide containing layer 26 may have a thicknessranging from 1 nm to 10 nm. In some examples, the oxide containing layer26 has a thickness ranging from 2 nm to 5 nm.

In one embodiment, the amorphous semiconductor containing layer 27 maybe composed of amorphous hydrogenated silicon (a-Si:H). In oneembodiment, an amorphous semiconductor material is a non-crystallinematerial that lacks the long-range order characteristic of a crystal.Other examples of amorphous semiconductors that are suitable for theamorphous semiconductor containing layer 27 may include diamond-likecarbon (DLC, also known as amorphous hydrogenated carbon, α-C:H),α-Ge:H, α-SiGe:H, α-SiC:H, α-SiO:H, α-SiN:H and combinations thereof,wherein ‘α’ is amorphous and ‘H’ is hydrogenated. The amorphoussemiconductor containing layer 27 may be deposited using a CVD process,such as atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD) andplasma enhanced CVD (PECVD), metal organic CVD (MOCVD) or combinationsthereof. The amorphous semiconductor containing layer 27 may also beformed using chemical solution deposition or a spin-on glass process.The amorphous semiconductor containing layer 27 may have a thicknessranging from 5 nm and 80 nm. In another example, the amorphoussemiconductor containing layer 27 has a thickness ranging from 10 nm to70 nm.

The metal nitride layer 28 may be composed of TiAl, TaN, TiN, HfN orcombinations thereof. The metal nitride layer 28 may be deposited usinga physical vapor deposition (PVD) process, such as sputtering and/orplating. Examples of sputtering apparatus that may be suitable fordepositing the n-type work function metal layer include DC diode typesystems, radio frequency (RF) sputtering, magnetron sputtering, andionized metal plasma (IMP) sputtering. In one example, in which themetal nitride layer 28 is composed of titanium nitride (TiN), the TiN issputtered from a solid titanium target, in which the nitrogen content ofthe metal nitride layer 28 is introduced by a nitrogen gas. In additionto physical vapor deposition (PVD) techniques, the metal nitride layer28 may also be formed using chemical vapor deposition (CVD) and atomiclayer deposition (ALD). The metal nitride layer 28 may have a thicknessranging from 1 nm to 10 nm. In some examples, the metal nitride layer 28has a thickness ranging from 2 nm to 5 nm.

The organic planarizing layer 29 or a layer of material that is capableof providing planarization may be formed through deposition. The organicplanarization layer 29 is typically composed of a polymer. For example,when metal nitride layer 28 is composed of titanium nitride (TiN), theorganic planarization layer 29 may be an amorphous carbon layer. Theorganic planarization layer 29 may be deposited using spin on depositionor chemical solution deposition. The organic planarization layer 29 mayhave a thickness ranging from 10 nm to 400 nm. In another embodiment,the organic planarization layer 29 may have a thickness ranging from 50nm to 100 nm. In some embodiments, following deposition, the organicplanarization layer 29 may be planarized by a process, such as chemicalmechanical planarization, to provide an upper surface that issubstantially planar.

In one embodiment, the SIT material layer stack 25 may include an oxidecontaining layer 26 of silicon oxide, an amorphous semiconductorcontaining layer 27 of amorphous hydrogenated silicon, a metal nitridelayer 28 of titanium nitride, and an organic planarizing layer 29 ofamorphous carbon.

Still referring to FIGS. 4A and 4B, in some embodiments, an etch mask 30may be formed over the SIT material layer stack 25. The etch mask 30 maybe positioned on the portions of the SIT material layer stack 25 thatare overlying the channel region portion of the fin structures 10. Theetch mask 30 is positioned to define the mandrel portion of thesacrificial structure, which dictates the pitch for the subsequentlyformed gate structures, i.e., gate structure pitch. The gate structurepitch is the center to center distance separating adjacent gatestructures to the adjacent fin structures 10. The mandrel portion of thesacrificial structure also dictates the dimensions and geometry of thegate structure. As will be described in more detail below, the spacermask portion of the sacrificial structure is formed on the sidewall ofthe mandrel portion of the sacrificial structure. The spacer maskportion dictates the positioning, geometry and dimensions of the laterformed gate sidewall spacers. Therefore, because the structure, i.e.,the spacer mask portion, that dictates the geometry and positioning ofthe gate sidewall spacers is formed in direct contact with thestructure, i.e., the mandrel portion, that dictates the positioning andgeometry of the gate structure, the gate sidewall spacers areself-aligned to the gate structure. Further, as will be described infurther detail below, the gate sidewall spacers dictates the positioningof the fin structure sidewalls that the epitaxial source and drain mergeregions are formed on. The epitaxial source and drain merge regions areself aligned to the gate sidewall spacers. Therefore, because the gatesidewall spacers are self aligned to the gate structure, and theepitaxial source and drain merge regions are self aligned to the gatesidewall spacers, the epitaxial source and drain merge regions are selfaligned to the gate structure.

In some embodiments, the alignment of the gate structure, the gatesidewall spacers and the epitaxial source and drain merge regions arebased on the formation of the mandrel portion of the sacrificialstructure from the SIT material layer stack 25 that is formed using thesingle etch mask 30 that is depicted in FIGS. 4A and 4B. The term“single etch mask” as used to describe the process sequence for formingthe gate structure, gate sidewall spacer, and epitaxial source and drainmerge regions means that only one photoresist mask is used in theformation of these structures. By reducing the number of photoresistmasks, and corresponding subsequent etch processes, the methods andstructures disclosed herein can reduce the fin erosion that typicallyresults from the etch processes for removing a dummy gate structure andgate sidewall spacer formation as used in prior finFET formationmethods. Further, the methods and structures disclosed herein reduce theconcentration of defects in the source and drain epitaxial mergeregions, and minimizes the formation of epitaxial nodules at the gatecorners.

In some embodiments, prior to forming the etch mask 30, ananti-reflection coating 31 is formed on the upper surface of the SITmaterial layer stack 25, e.g., is formed on the upper surface of theorganic planarization layer 29. The anti-reflection coating 31 mayinclude silicon (Si) and thus may be referred to as a “SiARC layer”. Theanti-reflection coating 31 may be deposited using spin on deposition,and may have a thickness ranging from 20 nm to 100 nm.

Forming the etch mask 30 may include deposition, photolithography anddevelopment processes. For example, the etch mask 30 may be provided bya blanket layer of photoresist material that is formed utilizing adeposition process such as, e.g., chemical vapor deposition, plasmaenhanced chemical vapor deposition, evaporation or spin-on coating. Theblanket layer of photoresist material is then patterned to provide thephotoresist mask utilizing a lithographic process that may includeexposing the photoresist material to a pattern of radiation anddeveloping the exposed photoresist material utilizing a resistdeveloper.

Along a cross-section that is parallel to the length of the finstructures, the pitch P2, i.e., center to center distance of a repeatingstructure of the etch mask may range from 40 nm to 80 nm, as depicted inFIG. 4B. In another embodiment, the pitch P2 of the repeating structureof the etch mask may range from 50 nm to 70 nm.

FIGS. 5A and 5B depict one embodiment of patterning a mandrel portion27′, 28′ of the sacrificial structure from the SIT material layer stack25. In one embodiment, the SIT material layer stack 25 is patterned andetched selectively to the etch mask 30. As used herein, the term“selective” in reference to a material removal process denotes that therate of material removal for a first material is greater than the rateof removal for at least another material of the structure to which thematerial removal process is being applied. For example, in oneembodiment, a selective etch may include an etch chemistry that removesa first material selectively to a second material by a ratio of 100:1 orgreater, e.g., 1000:1. In one embodiment, the etch process forpatterning the mandrel portion 27′, 28′ of the sacrificial structurefrom the SIT material layer stack 25 includes a first etch sequence forremoving the exposed portions of the antireflective coating 31, theplanarization layer 29, the metal nitride layer 28, and the amorphoussemiconductor layer 27 selectively to the etch mask 30 and the oxidecontaining layer 26. In some embodiments, the etch process forpatterning the mandrel portion 27′, 28′ of the sacrificial structurefrom the SIT material layer stack 25 includes an anisotropic etchprocess. One example of an anisotropic etch process for forming themandrel portion 27′, 28′ of the sacrificial structure from the SITmaterial layer stack 25 includes reactive ion etching. Reactive ionetching (RIE) is a form of plasma etching in which during etching thesurface to be etched is placed on the RF powered electrode. Moreover,during RIE the surface to be etched takes on a potential thataccelerates the etching species extracted from plasma toward thesurface, in which the chemical etching reaction is taking place in thedirection normal to the surface. Other examples of anisotropic etchingthat can be used at this point of the present disclosure include ionbeam etching, plasma etching or laser ablation.

In some embodiments, the etch process sequence for forming the mandrelportion 27′, 28′ of the SIT material layer stack 25 removes the etchmask 30, the antireflective coating 31, and the planarization layer 29in their entirety. The mandrel portion 27′, 28′ of the SIT materiallayer stack 25 includes a remaining portion of the metal nitride layer28′ and a remaining portion of the amorphous semiconductor layer 27′. Insome embodiments, the mandrel portion 27′, 28′ of the SIT material layerstack 25 has a width W2 ranging from 20 nm to 30 nm. Along across-section that is parallel to the length of the fin structures thepitch P3 separating adjacent mandrel portions 27′, 28′ of the SITmaterial layer stack 25 may range from 40 nm to 80 nm.

FIGS. 6A and 6B depict one embodiment of forming a spacer mask portion35 of the sacrificial structure on the mandrel portion 27′, 28′ of thesacrificial structure. The spacer mask portion 35 is typically formed onat least the sidewalls of the mandrel portion 27′, 28′ of thesacrificial structure. In some embodiments, a portion of the spacer maskportion 35 is typically formed on an upper surface of the mandrelportion 27′, 28′ of the sacrificial structure. The spacer mask portion35 may be a conformally deposited continuous layer that is present onthe sidewalls and upper surface of the mandrel portion 27′, 28′ of thesacrificial structure. The term “conformal” denotes a layer having athickness that does not deviate from greater than or less than 30% of anaverage value for the thickness of the layer. The thickness of thespacer mask portion 35 that is present on the sidewalls of the mandrelportion 27′, 28′ of the sacrificial structure typically dictates thewidth of the subsequently formed gate sidewall spacers. In someembodiments, to provide gate sidewall spacers having a width rangingfrom 2 nm to 5 nm, the thickness of the spacer mask portion 35 may rangefrom 2 nm to 5 nm. The spacer mask portion 35 may be composed of a metalnitride containing material. For example, the spacer mask portion 35 maybe composed of WN, TaN, TiN, HfN or combinations thereof. Thecomposition of the spacer mask portion 35 may be the same of differentfrom the composition of the remaining portion of the metal nitride layer28′ in the mandrel portion 27′, 28′ of the sacrificial structure. Thespacer mask portion 35 may be formed using physical vapor depositionprocesses, such as plating and/or sputter, or may be formed usingchemical vapor deposition processes, such as plasma enhanced chemicalvapor deposition and/or atomic layer deposition. In one example, thespacer mask portion 35 is composed of titanium nitride that is formedusing atomic layer deposition (ALD).

FIGS. 6A and 6B further depict etching the deposited material layer thatprovides the spacer mask portion 35 so that a remaining portion of thespacer mask portion 35 remains only on the sidewalls and optionally theupper surface of the mandrel portion 27′, 28′ of the sacrificialstructure. The horizontal portions of the deposited material layer thatprovides the spacer mask portion 35 that is present on the upper surfaceof the oxide containing layer 26 may be removed by an etch process, suchas anisotropic etch, e.g., reactive ion etch (RIE). It is noted that aportion of the material layer that provides the spacer mask portion 35may be present on the upper surface of the mandrel portion 27′, 28′ ofthe sacrificial structure following the etch process that removes thehorizontal portions of the material layer for the spacer mask portion 35on the oxide containing layer 26. In other embodiments, the portion ofthe material layer that provides the spacer mask portion 35 that ispresent on the upper surface of the mandrel portion 27′, 28′ of thesacrificial structure is removed. In this embodiment, the spacer maskportion 35 is present only on the sidewalls of the mandrel portion 27′,28′ of the sacrificial structure, and the remaining portion of the metalnitride layer 28′ is exposed as the upper surface of the sacrificialstructure.

FIGS. 7A and 7B depict one embodiment of etching the at least onedielectric layer 20 using the sacrificial structure as an etch mask. Insome embodiments, the width W3 extending from an exterior sidewall S1 ofspacer mask portion 35 on one side of the mandrel portion 27′, 28′ tothe exterior sidewall S2 of the spacer mask portion 35 on the other sideof the mandrel portion 27′, 28′ provides the exterior dimensions of thegate sidewall spacer. In some embodiments, the etch process for etchingthe at least one dielectric layer 20 also removes the exposed portionsof the oxide containing layer 26. In some embodiments, the etch processremoves the material of the at least one dielectric layer 20 and theoxide containing layer 26 selectively to the material of the spacer maskportion 35. The etch process may be an anisotropic etch process, such asreactive ion etch (RIE), ion beam etching, plasma etching or laserablation.

In some embodiments, etch process may continue to remove the exposedportions of the fin structures 10, and expose a sidewall portion of thefin structures 10 that is aligned with the outer sidewall of the gatesidewall spacers formed from the remaining portion of the at least onedielectric layer 20. For example, the exposed portions of the finstructures 10 may be removed selectively by an etch that is selective tothe sacrificial structure and the isolation regions 15.

FIG. 8 depicts one embodiment of forming an epitaxial semiconductormaterial 40 on exposed sidewall S3 of the fin structure 5 that isaligned with the overlying etched sidewall S4, S5 of the remainingportion of the at least one dielectric layer 20. The epitaxialsemiconductor material 40 provides an epitaxial source region and anepitaxial drain region that are present on opposing sides of the channelregion portion of the fin structure 10. The terms “epitaxial growthand/or deposition” means the growth of a semiconductor material on adeposition surface of a semiconductor material, in which thesemiconductor material being grown has substantially the samecrystalline characteristics as the semiconductor material of thedeposition surface. The term “epitaxial material” denotes a materialthat is formed using epitaxial growth. In some embodiments, when thechemical reactants are controlled and the system parameters setcorrectly, the depositing atoms arrive at the deposition surface withsufficient energy to move around on the surface and orient themselves tothe crystal arrangement of the atoms of the deposition surface. Thus, insome examples, an epitaxial film deposited on a {100} crystal surfacewill take on a {100} orientation.

In some embodiments, the epitaxial semiconductor material 40 is formedon the exposed sidewall S3 of at least one of a source region portionand a drain region portion of the fin structures 10. In someembodiments, epitaxial deposition of the epitaxial semiconductormaterial 40 is a selective deposition process. For example, although theepitaxially deposited the epitaxial semiconductor material 40 orientatesto the crystal arrangement of a semiconductor material and is depositedthereon, such as the exposed sidewall surface S3 of the fin structures10, the epitaxial semiconductor material 40 may not be deposited on adielectric material. For example, the epitaxial semiconductor material40 is not formed on the at least one dielectric layer 20, and themandrel portion 27′, 28′ and the spacer mask portion 30 of thesacrificial structure.

In some embodiments, the epitaxial semiconductor material 40 may becomposed of a silicon-containing material. For example, the epitaxialsemiconductor material 40 may be composed of a base material entirely ofsilicon, i.e., not counting dopants for charge carriers. In otherembodiments, the epitaxial semiconductor material 40 is composed ofgermanium, silicon germanium, a silicon germanium and carbon alloy(e.g., silicon germanium doped with carbon (SiGe:C), germanium alloys,gallium arsenic, indium arsenic, indium phosphide, as well as otherIII/V and II/VI compound semiconductors. Examples of silicon includingsource gasses may include silane, disilane, trisilane, tetrasilane,hexachlorodisilane, tetrachlorosilane, dichlorosilane, trichlorosilane,methylsilane, dimethylsilane, ethylsilane, methyldisilane,dimethyldisilane, hexamethyldisilane and combinations thereof. Examplesof germanium including source gasses for epitaxially forming theepitaxial semiconductor material 40 of a germanium containingsemiconductor include germane, digermane, halogermane, dichlorogermane,trichlorogermane, tetrachlorogermane and combinations thereof.

Epitaxial deposition for forming the epitaxial semiconductor material 40may be carried out in a chemical vapor deposition apparatus, such as ametal organic chemical vapor deposition (MOCVD) apparatus or a plasmaenhanced chemical vapor deposition (PECVD) apparatus.

In some embodiments, the epitaxial semiconductor material 40 may bein-situ doped. By “doped” it is meant that the epitaxial semiconductormaterial 40 includes a p-type or n-type dopant present therein. Forexample, the concentration of the p-type or n-type dopant in theepitaxial semiconductor material 40 may range from 5×10²⁰ atoms/cm³ to8×10²⁰ atoms/cm³. In another example, the concentration of the p-type orn-type dopant in the epitaxial semiconductor material 40 may range from6×10²⁰ atoms/cm³ to 7×10²⁰ atoms/cm³. The term “in situ” denotes thatthe dopant, e.g., n-type or p-type dopant, is introduced to the basesemiconductor material, e.g., silicon or silicon germanium, during theformation of the base material. For example, an in situ doped epitaxialsemiconductor material may introduce n-type or p-type dopants to thematerial being formed during the epitaxial deposition process thatincludes n-type or p-type source gasses.

In one embodiment, the n-type gas dopant source may include arsine(AsH₃), phosphine (PH₃) and alkylphosphines, such as with the empiricalformula R_(x)PH_((3-x)), where R=methyl, ethyl, propyl or butyl and x=1,2 or 3. Alkylphosphines include trimethylphosphine ((CH₃)₃P),dimethylphosphine ((CH₃)₂PH), triethylphosphine ((CH₃CH₂)₃P) anddiethylphosphine ((CH₃CH₂)₂PH). The p-type gas dopant source may includediborane (B₂H₆). The source gas for the base material may be provided bygermane, digermane, halogermane, silane, disilane, trisilane,tetrasilane, hexachlorodisilane, tetrachlorosilane, dichlorosilane,trichlorosilane, methylsilane, dimethylsilane, ethylsilane,methyldisilane, dimethyldisilane, hexamethyldisilane and combinationsthereof.

The epitaxial semiconductor material 40 typically provides epitaxialsource and drain merge regions (also referred to as epitaxial source anddrain merge structures) between adjacent fin structures. By “merge” itis meant that the epitaxial semiconductor material 40 may be in directcontact with two adjacent fin structures 10. As used herein, the term“drain” means a doped region in semiconductor device located at the endof the channel, in which carriers are flowing out of the transistorthrough the drain. As used herein, the term “source” is a doped regionin the semiconductor device, in which majority carriers are flowing intothe channel. The “channel” is the region of the underlying the gatestructure and between the source and drain of a semiconductor devicethat becomes conductive when the semiconductor device is turned on.

In the embodiments in which the finFET device being formed has n-typesource and drain regions, and is referred to as an n-type finFET, thedoped epitaxial semiconductor material 40 is doped with an n-type dopantto have an n-type conductivity. In the embodiments in which the finFETdevice being formed has p-type source and drain regions, and is referredto as a p-type finFET, the doped epitaxial semiconductor material 40 isdoped with a p-type dopant to have a p-type conductivity. As usedherein, “p-type” refers to the addition of impurities to an intrinsicsemiconductor that creates deficiencies of valence electrons. In a typeIV semiconductor, such as silicon, examples of p-type dopants, i.e.,impurities, include but are not limited to, boron, aluminum, gallium andindium. As used herein, “n-type” refers to the addition of impuritiesthat contributes free electrons to an intrinsic semiconductor. In a typeIV semiconductor, such as silicon, examples of n-type dopants, i.e.,impurities, include but are not limited to antimony, arsenic andphosphorous.

In some embodiments, the n-type or p-type dopant is diffused, i.e.,driven, from the doped epitaxial semiconductor material 40 into a sourceand drain extension region in the fin structures 10. In one embodiment,the thermal annealing that diffuses the dopant from the doped epitaxialsemiconductor material 40 into the extension region portions of the finstructures 10 includes an annealing process selected from the groupconsisting of rapid thermal annealing (RTA), flash lamp annealing,furnace annealing, laser annealing and combinations thereof. In oneembodiment, the thermal annealing for driving the dopant, i.e., p-typeor n-type dopant, from doped epitaxial semiconductor material 40 intothe extension region portions of the fin structures 10 may include atemperature ranging from 800° C. to 1200° C., and a time period rangingfrom 10 milliseconds to 100 seconds.

FIG. 9 depicts one embodiment of forming a dielectric fill 45 betweenadjacent pillars of dielectric material that remains following etchingof the at least one dielectric layer 20 selectively to the mandrelportion 27′, 28′ and the spacer mask portion 35 of the sacrificialstructure. The dielectric fill 45 may be an oxide containing material.For example, the dielectric fill 45 may be silicon oxide (SiO₂). Otherexamples of materials that may be employed for the dielectric fill 45include silicon nitride, silicon oxynitride, hafnium oxide, hafniumoxynitride, alumina and combinations thereof. The dielectric fill 45 maybe formed using CVD, PECVD, high-density plasma CVD (HPCVD), chemicalsolution deposition or a spin-on glass process. Following deposition,the material for the dielectric fill 45 may be planarized so that theupper surface of the dielectric fill 45 is coplanar with the uppersurface of the upper surface of the sacrificial structure, i.e.,remaining portion of the metal nitride layer 27′ of the mandrel portion27′, 28′.

FIG. 10 depicts one embodiment of removing the mandrel portion 27′, 28of the sacrificial structure. In some embodiments, the remainingportions of the metal nitride layer 27′ and the amorphous semiconductorlayer 28′ that provide the mandrel portion 27′, 28′ of the sacrificialstructure may be removed by an etch process that is selective to thedielectric fill 45, the spacer mask portion 35 of the sacrificialstructure, and the oxide containing layer 26. The etch process forremoving the amorphous semiconductor layer 28′ may an anisotropic etch,such as reactive ion etch, or may be an isotropic etch, such as a wetchemical etch.

FIG. 11 depicts one embodiment of etching the remaining portion of theat least one dielectric layer 20 selectively to the spacer mask portion35 of the sacrificial structure to form the dielectric sidewall spacer50 of the subsequently formed gate structure. In some embodiments, theetch step for etching the remaining portion of the at least onedielectric layer 20 may also recess the dielectric fill 45. In oneembodiment, the etch process for etching the remaining portion of the atleast one dielectric layer 20 may be selective to the fin structures 20.The etch process for etching the remaining portion of the at least onedielectric layer 20 may be an anisotropic etch process. Examples ofanisotropic etch processes that are suitable for use at this stage ofthe process flow include reactive ion etch, ion beam etching, plasmaetching or laser ablation. The step of etching the remaining portion ofthe at least one dielectric layer using the spacer mask portion 35 ofthe sacrificial structure defines the interior sidewall of thedielectric sidewall spacer 50 and exposes the channel region portion ofthe fin structures 10. The width of the dielectric sidewall spacer 50 issubstantially equal to the width of the spacer mask portion 35 of thesacrificial structure.

FIG. 12 depicts one embodiment of removing the spacer mask portion 35 ofthe sacrificial structure. In some embodiments, the spacer mask portion35 may be removed by an etch process that is selective to at least thedielectric fill 45, the dielectric sidewall spacer 50 and the finstructures 10. In some embodiments, the spacer mask portion 35 may beremoved by an anisotropic etch or isotropic etch.

FIG. 13 depicts one embodiment of forming gate structures 60 on thechannel region portions of the fin structures 10 between the gatesidewall spacers 50 for each of the finFET semiconductor devices 100.The term “gate structure” means a structure used to control outputcurrent (i.e., flow of carriers in the channel) of a semiconductingdevice through electrical or magnetic fields. In one embodiment, each ofthe finFET devices 100 includes a gate structure 60 that may be composedof at least one gate dielectric layer 61 and at least one gate conductorlayer 62. The at least one gate dielectric layer 61 is composed of aninsulator, and is present between the channel region portion of the finstructure 10 and the at least one gate conductor layer 62 of the gatestructure 60.

The at least one gate dielectric layer 61 is typically positioned on atleast a channel region portion of the fin structures 10. In someembodiments, the at least one gate dielectric layer 61 is also formed onthe interior sidewalls of the gate sidewall spacer 50, to provide aU-shaped cross sectional geometry. The at least one gate dielectriclayer 61 may be formed by a thermal growth process such as, e.g.,oxidation, nitridation or oxynitridation. In other embodiments, the atleast one gate dielectric layer 61 may be formed using a depositionprocess, such as CVD. In some embodiments, the at least one gatedielectric layer 61 is composed of a low-k dielectric material, such assilicon oxide (SiO₂), which typically has a dielectric constant of lessthan 4.0 at room temperature, e.g. 25° C. In some embodiments, the atleast one gate dielectric 61 is composed of a high-k dielectricmaterial. High-k dielectric materials have a dielectric constant greaterthan silicon oxide (SiO₂) at room temperature, e.g., 25° C. For example,a high-k dielectric composed of hafnium oxide (HFO₂), may have adielectric constant of 4.0 or greater.

In one embodiment, the at least one gate dielectric layer 61 mayinclude, but is not limited to, an oxide, nitride, oxynitride and/orsilicates including metal silicates, aluminates, titanates and nitrides.In one example, when the at least one gate dielectric layer 61 iscomprised of an oxide, the oxide may be selected from the groupincluding, but not limited to, SiO₂, HfO₂, ZrO₂, Al₂O₃, TiO₂, La₂O₃,SrTiO₃, LaAlO₃, Y2O₃ and mixture thereof. The physical thickness of theat least one gate dielectric layer 61 may vary, but typically, the atleast one gate dielectric layer 61 has a thickness ranging from 1 nm to10 nm.

The at least one gate conductor layer 62 may be composed of polysilicon,SiGe, a silicide, a metal or a metal-silicon-nitride, such as Ta—Si—N.Examples of metals that can be used as the at least one gate conductorlayer 62 include, but are not limited to Al, W, Cu, Ti or other likeconductive metals. In some embodiments, the at least one gate conductorlayer 62 may be composed of a p-type work function metal layer and/or ann-type work function metal layer. As used herein, a “p-type workfunction metal layer” is a metal layer that effectuates a p-typethreshold voltage shift. In one embodiment, the work function of thep-type work function metal layer ranges from 4.9 eV to 5.2 eV. As usedherein, “threshold voltage” is the lowest attainable gate voltage thatwill turn on a semiconductor device, e.g., transistor, by making thechannel of the device conductive. The term “p-type threshold voltageshift” as used herein means a shift in the Fermi energy of a p-typesemiconductor device, e.g., a finFET having p-type conductivity sourceand drain regions, towards a valence band of silicon in the siliconcontaining substrate of the p-type semiconductor device. A “valenceband” is the highest range of electron energies where electrons arenormally present at absolute zero.

In one embodiment, the p-type work function metal layer may be composedof titanium and their nitrided/carbide. In one embodiment, the p-typework function metal layer is composed of titanium nitride (TiN). Thep-type work function metal layer may also be composed of TiAlN, Ru, Pt,Mo, Co and alloys and combinations thereof. In one embodiment, thep-type work function metal layer comprising titanium nitride (TiN) maybe deposited by a physical vapor deposition (PVD) method, such assputtering. Examples of sputtering apparatus that may be suitable fordepositing the p-type work function metal layer include DC diode typesystems, radio frequency (RF) sputtering, magnetron sputtering, andionized metal plasma (IMP) sputtering. In addition to physical vapordeposition (PVD) techniques, the p-type work function metal layer mayalso be formed using chemical vapor deposition (CVD) and atomic layerdeposition (ALD).

As used herein, an “n-type work function metal layer” is a metal layerthat effectuates an n-type threshold voltage shift. “N-type thresholdvoltage shift” as used herein means a shift in the Fermi energy of ann-type semiconductor device towards a conduction band of silicon in asilicon-containing substrate of the n-type semiconductor device, e.g., afinFET having n-type conductivity source and drain regions. The“conduction band” is the lowest lying electron energy band of the dopedmaterial that is not completely filled with electrons. In oneembodiment, the work function of the n-type work function metal layerranges from 4.1 eV to 4.3 eV. In one embodiment, the n-type workfunction metal layer is composed of at least one of TiAl, TaN, TiN, HfN,HfSi, or combinations thereof. The n-type work function metal layer canbe deposited using chemical vapor deposition (CVD), atomic layerdeposition (ALD), sputtering or plating. In one embodiment, the n-typework function metal layer is composed of titanium aluminum (TiAl) and isdeposited using sputtering. Examples of sputtering apparatus that may besuitable for depositing the n-type work function metal layer include DCdiode type systems, radio frequency (RF) sputtering, magnetronsputtering, and ionized metal plasma (IMP) sputtering. In one example,an n-type work function metal layer composed of TiN is sputtered from asolid titanium target, in which the nitrogen content of the metalnitride layer is introduced by a nitrogen gas. In another example, ann-type work function metal layer composed of TiN is sputtered from asolid target comprised of titanium and nitrogen. In addition to physicalvapor deposition (PVD) techniques, the n-type work function metal layermay also be formed using chemical vapor deposition (CVD) and atomiclayer deposition (ALD). The at least one second gate structure 44 may beformed using deposition, photolithography and etch processes.

The material for the at least one gate conductor 62 may be deposited tofill the space over the channel region portion of the fin structure 10within the interior sidewalls of the gate sidewall spacer 50. In someembodiments, a planarization process may be applied to the materialdeposited for the at least one gate conductor layer 62 so that an uppersurface of the at least one gate conductor layer 62 is substantiallycoplanar with an upper surface of the gate sidewall spacer 50. Thephysical thickness of the at least one gate conductor layer 62 may rangefrom 1 nm to 10 nm.

FIG. 14 is a perspective view of one embodiment of fin field effecttransistors formed using the method depicted in FIGS. 1-13.

Following formation of the at least one gate conductor layer 62,contacts (also referred to as interconnects) may be formed to the sourceand drain regions, i.e., epitaxial source and drain merge regions 40,and the gate structures 60. In some embodiments, a layer of dielectricmaterial can be blanket deposited atop the entire substrate andplanarized. The blanket dielectric may be selected from the groupconsisting of silicon-containing materials, such as SiO₂, Si₃N₄,SiO_(x)N_(y), SiC, SiCO, SiCOH, and SiCH compounds; the above-mentionedsilicon-containing materials with some or all of the Si replaced by Ge;carbon-doped oxides; inorganic oxides;

inorganic polymers; hybrid polymers; organic polymers such as polyamidesor SiLK™; other carbon-containing materials; organo-inorganic materialssuch as spin-on glasses and silsesquioxane-based materials; anddiamond-like carbon (DLC, also known as amorphous hydrogenated carbon,α-C:H). Additional choices for the blanket dielectric include any of theaforementioned materials in porous form, or in a form that changesduring processing to or from being porous and/or permeable to beingnon-porous and/or non-permeable. The deposited dielectric is thenpatterned and etched to form via holes to the various source/drain,e.g., doped epitaxial semiconductor material 40, and gate conductorregions, e.g., the least one gate conductor layer 62 of the gatestructure 60, of the device. Following via formation contacts (alsoreferred to interconnects) are formed by depositing a conductive metalinto the via holes using deposition methods, such as CVD or plating. Theconductive metal may include, but is not limited to, tungsten, copper,aluminum, silver, gold and alloys thereof.

In one embodiment, the methods described above can provide a finFETsemiconductor device that includes a gate structure 60 present on achannel region portion of a fin structure 10, wherein the gate structure60 includes a gate sidewall spacer 50 contacting a sidewall of the atleast one gate dielectric 61 and the at least one gate conductor 62. Anepitaxial source region and an epitaxial drain region (provided by theepitaxial semiconductor material 40) is present on opposing sidewalls ofthe fin structure 10.

FIG. 15 is a magnified view of section C1 in FIG. 13. FIG. 15 depictsthat the sidewall surfaces S7 of the epitaxial source region and theepitaxial drain region, i.e., epitaxial semiconductor material 40, thatare in contact with the sidewalls of the fin structure 10 are alignedwith an outside surface S5 of the gate sidewall spacer 50. The gatestructure 61, 62 is in direct contact with the interior sidewall S6 ofthe gate sidewall spacer 50. The gate structure 10, the gate sidewallspacers 50 and the epitaxial source and drain regions i.e., epitaxialsemiconductor material 40, are formed using a single sidewall imagetransfer (SIT) process employing the mandrel portion 27′, 28′ of thesacrificial structure that is formed using the single etch mask 30 thatis depicted in FIGS. 4A and 4B. Therefore, because a single etch mask 30is used to form the gate structure 10, the gate sidewall spacers 50 andthe epitaxial source and drain regions, i.e., epitaxial semiconductormaterial 40, the gate sidewall spacer 50, the gate dielectric 61, andthe gate conductor 62 are self-aligned to one another.

While the methods and structures of the present disclosure have beenparticularly shown and described with respect to preferred embodimentsthereof, it will be understood by those skilled in the art that theforegoing and other changes in forms and details may be made withoutdeparting from the spirit and scope of the present disclosure. It istherefore intended that the present disclosure not be limited to theexact forms and details described and illustrated, but fall within thescope of the appended claims.

What is claimed is:
 1. A method of forming a semiconductor devicecomprising: depositing a dielectric layer over a fin structure; forminga sacrificial structure on a portion of the dielectric layer, saidsacrificial structure including a mandrel portion and a spacer maskportion; forming source and drain structures on opposing sides of aportion of the fin structure that the sacrificial structure is presenton; removing the mandrel portion of the sacrificial structure; etchingthe dielectric layer selective to the spacer mask portion, wherein aremaining portion of the dielectric layer provides a gate sidewallspacer on opposing sides of the fin structure; and forming a gatestructure on a channel region portion of the fin structure, wherein thegate structure is in direct contact with the gate sidewall spacer. 2.The method of claim 1, wherein only a single photoresist mask is used ina sequence to form the gate structure, the gate sidewall spacer and thesource and drain structures.
 3. The method of claim 1, wherein theforming of the sacrificial structure on the dielectric layer comprises:forming the mandrel portion of a first material on the dielectric layer,wherein the mandrel portion is over the fin structure; and forming aconformal layer of a second material on at least sidewalls of themandrel portion, wherein the conformal layer provides the spacer maskportion of the sacrificial structure, and the first material may beetched selectively to the second material.
 4. The method of claim 3further comprising etching the fin structure selectively to the mandrelstructure.
 5. The method of claim 4, wherein the forming of the mandrelportion of the first material comprises: depositing a semiconductorincluding material layer on the dielectric layer; forming a photoresistetch mask over the semiconductor including material layer; etching thesemiconductor including material layer selectively to the photoresistetch mask and the dielectric layer; and removing the photoresist etchmask.
 6. The method of claim 1, wherein the forming of the source anddrain structures on opposing sides of the portion of the fin structurethat the sacrificial structure is present on comprises epitaxialdeposition of a semiconductor material that is in-situ doped to ann-type or p-type conductivity.
 7. The method of claim 6, wherein thesource and drain structures are formed on a sidewall portion of the finstructure.
 8. The method of claim 1, wherein removing the mandrelportion of the sacrificial structure comprises an etch process that isselective to the spacer mask portion.
 9. The method of claim 1, whereinthe etching of the dielectric stack selective to the spacer mask portioncomprises an anisotropic etch process that is also selective to the finstructure.
 10. The method of claim 1, wherein the forming of the gatestructure comprises forming a high-k gate dielectric on the channelregion portion of the fin structure and forming a metal gate conductoron the high-k gate dielectric.
 11. A method of forming a semiconductordevice comprising: depositing a dielectric layer over a plurality of finstructures; forming a plurality of sacrificial structures on a portionof the dielectric layer, wherein each sacrificial structure of saidplurality of sacrificial structures includes a mandrel portion and aspacer mask portion; etching the plurality of fin structures selectivelyto the plurality of sacrificial structures to expose a sidewall portionof the plurality of fin structures; forming source and drain structureson the sidewall portion of the plurality of fin structures; removing themandrel portion of the plurality of sacrificial structures; etching thedielectric layer selective to the spacer mask portion, wherein aremaining portion of the dielectric layer provides gate sidewallspacers; and forming a gate structure on the channel region portion ofthe plurality of fin structures, wherein the gate structure is incontact with the gate sidewall spacers.
 12. The method of claim 11,wherein only a single photoresist mask is used in a sequence to form thegate structure, the gate sidewall spacers and the source and drainstructures.
 13. The method of claim 11, wherein the forming of theplurality of sacrificial structures on the portion of the dielectriclayer comprises: forming the mandrel portion of a first material of thesacrificial structure on the dielectric layer, wherein the mandrelportion is over the fin structure; and forming a conformal layer of asecond material on at least sidewalls of the mandrel portion, whereinthe conformal layer provides the spacer mask portion of the sacrificialstructure, and the first material may be etched selectively to thesecond material.
 14. The method of claim 13, wherein removing themandrel portion of the plurality of sacrificial structures comprises anetch process that is selective to the spacer mask portion, and whereinthe etching of the dielectric layer selective to the spacer mask portioncomprises an anisotropic etch process that is also selective to theplurality of fin structures.
 15. The method of claim 13, wherein theforming of the gate structure on the plurality of fin comprises forminga high-k gate dielectric on the channel region portion of the pluralityof fin structures and forming a metal gate conductor on the high-k gatedielectric.
 16. A semiconductor device comprising: a gate structurepresent on a channel portion of a fin structure, wherein the gatestructure includes a dielectric spacer contacting a sidewall of a gatedielectric and a gate conductor; and an epitaxial source region and anepitaxial drain region present on opposing sidewalls of the finstructure, wherein surfaces of the epitaxial source region and theepitaxial drain region that are in contact with the sidewalls of the finstructure are aligned with an outside surface of the dielectric spacer.17. The semiconductor device of claim 16, wherein the dielectric spacer,the gate dielectric, and the gate conductor are self-aligned to oneanother.
 18. The semiconductor device of claim 17, wherein thedielectric spacer, the gate dielectric, and the gate conductor areformed in a single photoresist mask sequence.
 19. The semiconductordevice of claim 16, wherein the gate conductor is comprised of a metal.20. The semiconductor device of claim 16, wherein the gate dielectric iscomprised of a high-k gate dielectric.